1. Field Of The Invention
The present invention relates to an aromatic polycarbonate-styrene polymer resin composition. More particularly, the present invention is concerned with an aromatic polycarbonate-styrene polymer resin composition comprising an aromatic polycarbonate; a specific rubber-modified styrene polymer; and a compatibility agent which is a specific copolymer containing an aromatic vinyl monomer and which has a non-uniform distribution with respect to the proportions of component monomers constituting the copolymer, so that the copolymer comprises copolymer molecules having different solubility parameter (SP) values, wherein the difference in SP value between the copolymer molecule having a maximum SP value and the copolymer molecule having a minimum SP value is within a specific range, and wherein the copolymer has an average SP value within a specific range. The aromatic polycarbonate-styrene polymer resin composition of the present invention has not only excellent impact strength and heat resistance, but also excellent melt flowability, which is a criterion for excellent molding processability.
The composition according to the present invention may further comprise a flame retardant, especially a phosphate, thereby providing a flame retardant resin composition which has an excellent flame retardancy as well as the above-mentioned excellent properties.
2. Prior Art
Due to their high impact resistance in addition to their high heat resistance, polycarbonate resin compositions obtained by incorporating a rubber-modified styrene polymer into a polycarbonate are widely used in various fields, such as the fields of parts for automobiles, household electrical appliances and office automation machines. However, such polycarbonate resin compositions having excellent impact resistance have a defect of being poor in melt flowability, and there have conventionally been problems in that it has not been possible to achieve both high impact resistance and high melt flowability at the same time.
In recent years, in the above-mentioned fields in which polycarbonate resin compositions are used, it has been desired that a polycarbonate resin composition be used for manufacturing small-thickness molded products and that the molding cycle time be reduced. Hence, there have been increasing demands for achieving an improvement in melt flowability while maintaining high impact resistance.
As prior art for providing polycarbonate resin compositions having an improved melt flowability, a technique of adding ABS resin (acrylonitrile/butadiene/styrene copolymer resin) or MBS resin (methyl methacrylate/butadiene/styrene copolymer resin) to polycarbonates (see Examined Japanese Patent Application Publication No. 38-15225) and a technique of adding polystyrene or rubber-modified polystyrene to polycarbonates (see Examined Japanese Patent Application Publication No. 43-6295) are known. However, the technique of adding an ABS resin or an MBS resin, although it brings about a dramatic improvement in impact strength, does not provide a satisfactory improvement in melt flowability. On the other hand, the technique of adding polystyrene or a rubber-modified polystyrene improves melt flowability but largely decreases impact strength, and hence has only a limited commercial application.
WO Publication No. 80/00027 discloses a resin composition comprising a polycarbonate, a polystyrene and an MBS resin (methyl methacrylate/butadiene/styrene copolymer resin). Although the resin composition of the above-mentioned publication has a high melt flowability, it has extremely low impact strength.
Unexamined Japanese Patent Application Laid-Open Specification No. 2-228353 (corresponding to EP publication No. 379039) discloses a resin composition comprising an impact resistant styrene copolymer comprised of an ethylenically unsaturated nitrile, an olefinic elastomer and styrene, an aromatic polycarbonate and a compatibility agent comprised of a core-shell type elastomer, the compatibility agent being intended to improve the compatibility between the impact resistant styrene copolymer and the aromatic polycarbonate. However, the resin composition of the above-mentioned Laid-Open Specification has a low melt flowability and a low impact strength and, therefore, poses many practical problems.
As prior art techniques for imparting flame retardancy to a polycarbonate resin, there are known, for example, a resin composition comprising a polycarbonate, an ABS resin, an organic phosphorus compound and a tetrafluoroethylene polymer (see Unexamined Japanese Patent Application Laid-Open Specification No. 2-32154), a resin composition comprising a polycarbonate, an ABS resin and a polyphosphate (see Unexamined Japanese Patent Application Laid-Open Specification No. 2-115262, corresponding to U.S. Pat. No. 5,204,394), and a resin composition comprising 50 to 90% by weight of a polycarbonate, 3 to 25% by weight of a polyphenylene ether, an ABS resin, a styrene polymer, and optionally an organic phosphorus compound and a polytetrafluoroethylene (see German Patent Application Publication No. 4200247). However, the resin compositions described in the above-mentioned publications have not only low melt flowability and low impact resistance, but are also unsatisfactory in flame retardancy and, therefore, the commercial applicability of these resin compositions is limited.
As described above, a polycarbonate resin composition simultaneously having both high melt flowability and impact strength has not been conventionally known, so that the development of such a composition and of a composition further having flame retardancy has been strongly desired.